DIGESTION AND ENDODERM OF LIMNOCODIUM. 119 
On the INTRA-CELLULAR DicEsTION aud KNpoperM of Limnoco- 
pium. By HK. Ray Lanxester, M.A., F. R.S. With Plates 
Wir, 1X. 
No observation made within the last three years appears to 
me to have greater importance and general significance for the 
progress of Biology than the discovery of the inception of solid 
food particles by endoderm cells im the Planarians and Nemato- 
phorous Ceelentera, by Elias Metschnikoff. 
The actual history of this discovery appears to date from the 
observations of Lieberkiihn on Spongilla (‘ Miiller’s Archiv,’ 1857). 
The first observer to suggest the existence of intra-cellular 
digestion in an organism other than one of the Protozoa or of the 
Porifera, was Allman, who, in his memoir on Myriothela (‘ Philo- 
soph. Transact.,’ vol. 165, 1875, p. 552), describes a thin layer of 
protoplasm as occurring on the free surface of the endoderm, 
and observes that “its occurrence, with its pseudopodial exten- 
sions, on the gastric surface of the animal, is full of interest, and 
suggests a close analogy between the absorptive action of the 
gastric surface and amceboid reception of nutriment.” 
Next we have a note by Metschnikoff in the ‘ Zoolog. 
Anzeiger,’ 1878, p. 387, in which the inception of solid food 
particles by the cells lining the alimentary canal of certain 
Planarians is described, and in the ‘Zeitsch. wiss. Zoologie,’ 
1879, p. 371, the same author describes similar observations 
on Sponges. 
Led by these observations of Metschnikoff, Jeffery Parker came 
to the conclusion that a similar mode of digestion obtains in 
Hydra. In his paper on the histology of Hydra fusca, published 
in the ‘Proceedings of the Royal Society,’ 1880, and in this 
Journal, April, 1880, Parker carefully describes the amceboid 
character of the endoderm cells of Hydra as seen in sections, 
the extent and activity of their movements during life having 
been previously insufficiently recognised. Dark-coloured irregu- 
lar granules of various sizes are found within these cells, and 
were noted by Kleinenberg to vary in number with the state of 
nutrition of the animal. Parker is convinced that these bodies 
are food particles, taken into the protoplasm of the cells, from 
the partially disintegrated bodies of the Entomostraca in the 
digestive cavity. The clearest case of ingestion of solid particles 
observed by Parker was when a diatom was seen to be com- 
pletely embedded in the protoplasm of a cell. Parker very 
judiciously observes that it is quite possible that a preliminary 
